LONDON -- The final report on an internal BBC probe is expected to state that late radio and TV host Jimmy Savile sexually abused "many hundreds and potentially up to 1,000 people" while working for the U.K. public broadcaster, the Guardian's sister publication The Observer reported.

At least 138 victims are believed to be pursuing civil actions against the BBC, according to the newspaper report. Last year, a police report cited 214 abuse cases and about 450 overall complaints recorded by authorities.

The BBC report is also set to call on the broadcaster's leadership to reform a "culture of secrecy," according to the paper.

Savile, who died in 2011, was host of TV chart show Top of the Pops and a DJ for the BBC's Radio 1. Late in 2012, abuse claims against him became public, causing a crisis at the BBC.

Former court of appeal judge Janet Smith has been working on a report for the BBC about the extent of the abuse and how the broadcaster could avoid similar problems in the future.

The final report, expected to come out next month, will emphasize that the exact number of Savile victims may never be known, according to the Observer. But it will also emphasize that BBC executives were aware of at least some cases, but took no action, it said, citing a source familiar with the probe behind the final report. That source also said that the extent of abuse was "shocking."

Representatives for the BBC Trust, the governing body of the broadcaster, and the BBC's management didn't immediately comment on the upcoming Smith report or the Observer article.